Pressure relief device for fuel pumps



1965 o. 5.. STEVENS ETAL 3,168,

PRESSURE RELIEF DEVICE FOR FUEL PUMPS Filed June 1'7, 1963 mdnmfiow.Uavzd .Ev. EZEVETZE' Eu EI'IE Shermezster 9 i k. Q

United States Patent Ofifice 3,168,044 Patented Feb. 2, 1965 3,168,044PRESSURE RELIEF DEVICE FOR FUEL PUMPS David B. Stevens, Mequon, andEugene Shermeister, Sheboygan, Wis. (both of Rte. 2, Box 449A,Thiensville, Wis.

Filed June 17, 1963, Ser. No. 288,299 '2 Claims. (Cl. 103-41) Thisinvention relates to pressure relief devices and has as its purpose toprovide means for quickly relieving pressure in the fuel line leadingfrom the fuel pump to the carburetor of an automobile engine when theengine is stopped.

Automobile engines are now practically universally equipped withengine-driven fuel pumps which pump fuel from the supply tank to thecarburetor of the engine; and while the pumps used on different enginesmay vary in design and construction, they all have an inlet connectiblewith the fuel supply tank and an outlet which connects with thecarburetor, and in all cases during operation of the pump suction ismanifested at its inlet and pressure exists in its outlet.

When the engine ignition is turned off to stop the engine, no furtherfuel should be delivered to the carburetor or from it to the intakemanifold, but heretofore the residual pressure which existed at theoutlet of the fuel pump when the ignition was turned off always forcedsome fuel into the carburetor. This resulted in an overly rich mixturebeing present in the carburetor the next time the engine was started,and made it difficult to start the engine. In addition, this pumping offuel after the ignition was shut 01f wasted a significant amount offuel.

Although this problem has been recognized for years and many attemptshave been made to cope with it, heretofore all expedients intended forthe purpose have been costly, complicated, and generally unsatisfactory.By contrast, this invention solves the problem by means of a simpleby-pass connection around the fuel pump from its inlet to its outlet,which though effective at all times, nevertheless does not interferewith proper delivery of fuel to the carburetor during operation of thepump.

With the above and other objects in view which will appear as thedescription proceeds, this invention resides in the novel construction,combination and arrangement of parts substantially as hereinafterdescribed and more particularly defined by the appended claims, it beingunderstood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawing illustrates one complete example of thephysical embodiment of the invention constructed according to the bestmode so far devised for the practical application of the principlesthereof, and in which:

FIGURE 1 is a vertical sectional view through a conventional fuel pumpequipped with the pressure relief device of this invention; and

FIGURE 2 is a fragmentary enlarged detail cross sectional view throughFIGURE 1 on the plane of the line 22.

Referring now particularly to the accompanying drawing, the numeral 5designates a fuel pump which may be considered representative of thoseemployed on automobile engines to pump fuel from the fuel tank of theautomobile (not shown) to the carburetor of the engine (also not shown).The specific construction of the fuel pump forms no part of thisinvention, but as in all such fuel pumps the one illustrated has aninlet 6 which is connectible through a line 7 with the fuel tank (notshown), an outlet 8 connectible through a line 9 with the carburetor ofthe engine (also not shown), and a diaphragm 10, flexure of whichalternately draws fuel through the inlet 6 into the pump and expels thesame under pressure through the outlet 8. Suitable inlet and outletvalves 11 and 12 are provided to enable the diaphragm to perform itspumping function.

The diaphragm 10 is pulled downwardly to draw fuel into the pump by acam 13 on a rotating shaft 14 of the engine acting through a lever 15pivoted as at 16 and connected with the diaphragm through a plunger 17.As the cam rotates and the lever 15 rides onto the low point thereon, acompression spring 18 hearing against the underside of the diaphragmforces the same upwardly to expel the fuel from the pump through theoutlet 8 and, in so doing, establishes a pressure zone at the outlet.

Without the benefit of this invention the residual pressure in theoutlet 8 which obtains at the instant the engine stops is suflicient tocause an appreciable amount of fuel to be delivered to the carburetor,thereby flooding the carburetor and perhaps also forcing some of thisraw fuel into the intake manifold. In any event, when the engine isagain started, this excess fuel in the carburetor produces an overlyrich mixture which makes starting diflicult and also wastes fuel.

To eliminate this objection the inlet 6 and the outlet 8 of the fuelpump are interconnected by duct means, indicated generally by thenumeral 20. This duct means is so designed and constructed that althoughit is at all times open and capable of returning fuel from the outlet tothe inlet or suction side of the pump and in a few seconds will soreturn all fuel under pressure in the outlet of the pump when theignition for the engine is shut off, it does not interfere with adequateand proper delivery of fuel to the carburetor during operation of thepump.

Specifically, the duct means 20 comprises two identical pipe couplings21, one of which is threaded into the inlet port and the other into theoutlet port of the pump, and each of which is adapted to have itsrespective fuel line 7-9 attached thereto in the conventional manner.

Each fitting 21 also has a nipple 22 secured in its side and projectingtherefrom. Preferably the nipples are driven into slightly undersizedholes in the fittings; but, in any event, their connections with thefittings must be fluid tight and to this end a sealing compound 23 orthe like may be applied around the base of the nipples where they jointhe fittings.

A flexible tube, desirably of a plastic material which is impervious togasoline, has its opposite end portions snugly telescoped over thenipples. If desired, clamps (not shown) may be applied to the endportions of the tube to assure against detachment from the nipples; butif the outer ends of the nipples are flared, as at 25, and the tube 24is made of a material which retains its resilience, clamps are notnecessary.

At least one of the nipples-and preferably bothhave a constriction 26 inthe bore thereof; and while this constriction may be located anywherealong the length of the nipple bore, it is most conveniently placed atthe inner end of the nipple where it can be formed by simply compressingor shrinking the end portion of the nipple.

Since a fuel pump in normal operation ordinarily de livers approximatelysixty gallons per hour, the constriction 26or, more accurately, theeffect of the constriction 26should be such that it will not reduce theflow by more than on the order of three and one-half percent. This wouldbe a reduction in flow of about two gallons per hour. Such slightreduction in flow does not noticeably affect the operation andperformance of an automobile engine, but a more serious reduction willbegin to starve the engine at higher speeds. It has been found that ifthe constriction 26 provides a passage on the order of forty-thousandthsof an inch (.040") in diameter for the short distance involved inreducing the diameter of the end of the nipple, as shown, entirelysatisfactory results are obtained, and that to the extent indic'ated'thesize of the constriction and its length are critical factors.

From the foregoing description taken in connection with,

the accompanying drawing, it will be apparent to those skilled inthisart that this invention provides an extremely simple device foreliminating a very trying and troublesome condition which aifects mostall automobile en'- gines wherein the fuel is delivered to thecarburetor by an engine-driven fuel pump, since it avoids flooding thecarburetor fuel delivered thereto after ignition of the engineis'shutbif. V

Experience with the pressure relieving device of this invention has alsodemonstrated that, in city driving, which is characterized by numerousstarts and stops, asaving in fuel of as much as ten percent (10%) hasbeen achieved. What isclaimed as our invention is:

1. A device for relieving the pressure at the outlet of a fuel pump andreturning fuel 'thereat to the inletof'the pump, comprising: a "pair oftubular pipe fittings, each 20 having means for connecting the same witha port in a -fuel pump so that one of said fittings may be located atthe inlet of the fuel pump and the other at its outlet; a nippleembedded in each fitting and projecting laterally therefrom, saidnipples being secured to their respective fittings in a fluid-tightmanner and opening into the interior of the fittings; a tube'having itsopposite end portions telescoped onto and tightly secured to the nipplesso as to connect one fitting with the other; and a constriction in thebore of at least one of said nipples.

2. The pressure relieving device of claim l,'wherein said constrictionis located at the inner end of each nipple and forms an orifice on theorder of forty-thousandths of aninch in diameter.

References Cited in the file of this patent UNITED STATES PATENTS2,249,326 Rabe July 15, 1941 2,648,285 Johnson Aug. 11, 1953 2,693,114Tapp et a1. Nov. 2, 1954 2,763,253 Murrah Sept. 18, 1956

1. A DEVICE FOR RELIEVING THE PRESSURE AT THE OUTLET OF A FUEL PUMP ANDRETURNING FUEL THEREAT TO THE INLET OF THE PUMP, COMPRISING: A PAIR OFTUBULAR PIPE FITTINGS, EACH HAVING MEANS FOR CONNECTING THE SAME WITH APORT IN A FUEL PUMP SO THAT OF SAID FITTINGS MAY BE LOCATED AT THE INLETOF THE FUEL PUMP AND THE OTHER AT ITS OUTLET; A NIPPLE EMBEDDED IN EACHFITTING AND PROJECTING LATERALLY THEREFROM, SAID NIPPLES BEING SECUREDTO THRIE RESPECTIVE FITTINGS IN A FLUID-TIGHT MANNER AND OPENING INTOTHE INTERIOR OF THE FITTINGS; A TUBE HAVING ITS OPPOSITE END PORTIONSTELESCOPED ONTO AND TIGHTLY SECURED TO THE NIPPLES SO AS TO CONNECT ONEFITTING WITH THE OTHER; AND A CONSTRICTION IN THE BORE OF AT LEAST ONEOF SAID NIPPLES.